Hi, Le mardi 26 juin 2018 à 19:44 +0530, Subhashini Rao Beerisetty a écrit :
In the kernel code I see it supports CLOCK_REALTIME \ CLOCK_MONOTONIC \ CLOCK_MONOTONIC_RAW timestamps. Can someone explain what’s major difference between those three modes and when to use which one?
A generic answer could be found here: http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/time.h.html
I’ve N number of Linux machines in the network with the same software running. Basically I need to collect the timestamps in kernel mode in all the machines and then compare, which(either CLOCK_REALTIME or CLOCK_MONOTIC_RAW or MONOTONIC) one would be the correct way?
Probably none. Anyway, please find some hints below: None of the monotonic clocks can be used because they're not supposed to be synchronized accross the network You're left with CLOCK_REALTIME, which is not synchronized accross the network by default. So before doing timestamp comparison, you would need to setup time synchronisation between hosts on your network: NTP to synchronise hosts to the same seconds with couple of millisecond precision, PTP for sub millisecond precision. Time synchronisation is a tough problem but it's required if you want to be able to compare timestamp accross hosts in a network. Regards. -- Yann Droneaud OPTEYA